Stephanie Chen, former Writer-Producer for CNN, stated in her Aug. 28, 2009 CNN.com article titled "'John Schools' Try to Change Attitudes about Paid Sex":
"No comprehensive effort has been made to track the numbers, but experts estimate 1 million to 2 million prostitutes work in the United States. The FBI's 2007 Uniform Crime Report lists about 78,000 arrests for prostitution and commercialized vice, but experts say those numbers are extremely conservative because many sex workers and johns aren't caught."
The Prostitutes' Education Network stated in its article "Prostitution in The United States - The Statistics," posted on its website (accessed Aug. 28, 2013):
"It is difficult to estimate the number of persons who currently work, or have ever worked as prostitutes for many reasons including the various definitions of prostitution. National arrest figures [in the United States] range over 100,000. The National Task Force on Prostitution suggests that over one million people in the US have worked as prostitutes in the United States, or about 1% of American women."
John Potterat, Former Director of STD/AIDS Programs for El Paso County (Colorado) Department of Health & Environment, et al., wrote in the May 1990 Journal of Sex Research article titled "Estimating the Prevalence and Career Longevity of Prostitute Women":
"Analyzed data on the prevalence and career longevity of prostitute women in Colorado Springs during nearly 2 decades, starting in 1970... The density of full-time equivalent prostitutes (FTEPs) appears to be about 23 per 100,000 population. By extension to the nation, it is estimated that an average of about 84,000 women, or about 59,000 FTEPs, worked as prostitutes in the US annually during the 1980s."
Élaine Audet, Associate Editor, and Micheline Carrier, Founder and Editor, of Sisyphe.org, stated in their Nov. 30, 2004 article "Decriminalize Prostituted Women, Not Prostitution," posted on the Sisyphe.org website:
"In 2001, the number of prostitutes in the world is estimated at 40 million."
Jean Vandepitte, MD, et. al., in the June 2006 Sexually Transmitted Infections article "Estimates of the Number of Female Sex Workers in Different Regions of the World," wrote:
"In sub-Saharan Africa, the FSW [Female Sex Workers] prevalence [percent equals estimated number of FSW in an area multiplied by 100 and divided by the size of an area's female population between the ages of 15-49] in the capitals ranged between 0.7% and 4.3% and in other urban areas between 0.4% and 4.3%. Population surveys from this same region yielded even higher proportions of women involved in transactional sex. The national FSW prevalence in Asia ranged between 0.2% and 2.6%; in the ex-Russian Federation between 0.1% and 1.5%; in East Europe between 0.4% and 1.4%; in West Europe between 0.1% and 1.4%; and in Latin America between 0.2% and 7.4%...
[M]ost countries in the world do not know the size of this population group. The estimates of the prevalence of FSW presented in this paper show how important this hard-to-reach population group is in all parts of the world."